Course-finding instrument for navigators.



Nu. 645,653. Patented Mar, 20, I900. c. H. WHITE. COURSE FINDINGINSTRUMENT FOR NAVIGATOR S.

(Application filed Dec. 4, 1897. Renewed July 29, 1899.) (No Model.)

' STATES I union,

CHARLES H. WHITE, OF BALTIMORE, MARYLAND, ASSIGNOR OF ONE-HALF TOCHARLES M. STRUVEN, OF SAME PLACE.

COURSE-FINDING INSTRUMENT FOR NAVIGATOR SI- SPECIFICATION forming partof Letters Patent No. 645,653, dated March 20, 1900.

Application filed December 4, 1897. Renewed July 29, 1899. Serial No.725,546. (No model.)

To aZZ whom it may concern:

Be it known that I, CHARLES H. WHITE, of the city of Baltimore, in theState of Maryland, have invented certain Improvements in Course-FindingInstruments for Navigators, of which the following is a specification.

This invention relates to a device adapted for temporary application toa map or chart whereby a navigator may easily and readily ascertain thedirection to be sailed according to his mariners compass to make acertain point or position.

The said invention consists in a card on which is printed the points andfractions of points of the compass, with the central portion thereofopen or made of some transparent material and provided with a revolublepointer. To the pin in the center of the card to which the pointer ispivoted is loosely attached a fine cord, which is passed through an eyein an arm hinged to the head of the pointer, so that when the cord isdrawn tight and moved around the card the hand will be moved with it.

To fully understand the nature and object of the invention, it must beunderstood that all charts used by navigators have printed on them, invarious places, diagrams of the points of the inariners compass and apointer showing in degrees of a circle and in fractions of the points ofthe compass the variation of the magnetic needle from the true north atsuch positions on the chart.

Ordinarily when a navigator has ascertained by observation or otherwisehis position on the chart and desires to give to the wheelsman thecourse to be sailed until another observation is made he draws animaginary line between his present position and the next objectivepoint. He then by the aid of the parallel-ruler transfers that line tothe center of the nearest diagram of the points of the compass, or, inother words, draws a second imaginary line parallel with the firstthrough the center of the said diagram and intersecting the circle,which is divided into degrees or the points and fractions of the pointsof the compass. This gives him the course to be sailed, except that'thedirection has to be corrected by the variation of the magnetic needlefrom the true north, as

indicated by the pointer on the said diagram, and the deviation of theneedle from the magnetic north owing to local attraction. For instance,if the variation of the needle is, say, one point to the west thecompasscourse to be steered is one point to the east of the courseindicated by the parallel-ruler.

In the further description of the said invention which follows referenceis made to the accompanying drawings, forming a part hereof, and inwhich Figure 1 represents a part of the chart of the Chesapeake bay,showing Point Lookout and Smiths Point, which are at the entrance of thePotomac river, together with the card and its attachments which form thesubject of the present invention. Fig. 2 is a crosssection of the card,showing its construction. Fig. 3 is an edge View of the pivoted armbefore alluded to.

Referring now to the drawing, A represents a square piece of paper onwhich is printed the points and fractions of the points of the compass.paper, or that within the circle a, is cut out and the other partinclosed between two sheets of some transparent material, such ascelluloid, and the whole bound together by a metallic frame 0. In thecenter of the card, constructed as described, is secured a pin d, whichprojects above its upper surface, and over this pin is placed looselythe pointer B. Between the head 6 of the pin d and the upper surface ofthe pointer B is attached a line cord C, which is passed through aneyef, formed in the upturned end of the arm D, hinged to the head of thepointer. The connection between the arm D and the pointer is of such anature that some slight force is required to move the formerindependently of the latter, sothat the arm will remain in any positionwith reference to the pointer in which it is placed.

In the foregoing description I have described the preferred constructionof the card; but it is evident that various alterations may be madetherein without materially affecting its efiiciency.

The manner of using the invention is as follows: Thearm D is first setso that the angular distance between the pointer and the The centralportion of the 75 cord when extended through the eye of the said arm anddrawn taut will be equal to the reverse of the variation of the pointerfrom the true north, as indicated in the diagram on the chart nearest tothe ascertained position of the vessel. Now supposing the vessel to bein a position adjacent to and directly north of a buoyac off SmithsPoint and it is desired to sail directly to Point Lookout light, whichis indicated on the chart, the card is placed on the chart so that itscenter is directly over the present position of the vessel and its upperor lower edge parallel with an adjacent parallel of latitude describedon the chart. The cord is then extended so as to intersect the PointLookout light, when the pointer will give in points and fractions of apoint the correct compasscourse to be steered, provided the same iscorrected for the deviation of the needle by local attraction.

I claim as my invention- '1. A device for the purpose described,whichconsists of a card with the points of the mariners compass inscribedthereon, combined with a revolublepointer pivoted at the center of thecard, an adjustable arm projecting from the pointer, and a cord which isattached to the pivot of the pointer, and passes through the adjustablearm, whereby the angle of the pointer with reference to the cord whenthe same is stretched, may be changed to suit the variation of themagnetic needle from the true north,substantially as specified.

2. A device for the purpose described,which consists of a card with thepoints of the mariners compass inscribed thereon, combined with arevoluble pointer pivoted at the center of the card, an eyed arm pivotedto the said pointer, and a cord which is attached to the pivot of thepointer and passes through the eye of the arm, whereby the angle of thepointer with reference to the cord when the same is stretched, may hechanged to suit the variation of magnetic needle from the true north,substantially as specified.

CHARLES H. WHITE. \Vitnesses:

DANL. FISHER, WM. T. I'IoWAnn.

